The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
IEEE 802.11, 802.11a, 802.11b, 802.11g, 802.11h, 802.11n, 802.16, and 802.20, which are hereby incorporated by reference in their entirety, define operation and implementation of wireless local area networks (WLANs). These standards define modes of operation for WLANs, including ad-hoc and infrastructure.
Referring now to FIG. 1, a functional block diagram of an ad-hoc wireless network 100 is depicted. The ad-hoc wireless network 100 includes three wireless client stations 104-1, 104-2, and 104-3, although ad-hoc networks with two or more client stations are possible. The client stations 104 together form a basic service set (BSS), identified by a BSS identifier, BSSID. In an ad-hoc network, such as the ad-hoc wireless network 100, the client stations 104 communicate directly with each other as indicated by the arrows in FIG. 1.
A beacon is periodically transmitted by the client stations 104. The beacon includes a timestamp used for synchronization, a beacon interval, and capability information, such as supported transfer rates. After transmission of the beacon, there is an announcement traffic indication message (ATIM) window, the length of which is indicated by the beacon. During the ATIM window, a client station 104 can notify another client station 104 that traffic has been buffered for it.
A beacon interval specifies the amount of time before the next beacon will be transmitted. Based upon the beacon interval, client stations 104 can operate in a low power mode until the next beacon is expected. During low power mode, a client station 104 may power down components, such as transceivers, and/or alter operation to conserve power.
The client station 104 may not be able to transmit or receive data while in low power mode. The client station 104 will resume normal operation in order to receive the beacon, and will remain awake during the ATIM window. If the client station 104 receives or transmits based on a received ATIM, it will stay awake for the remainder of the beacon interval.
Referring now to FIG. 2, a functional block diagram of an exemplary infrastructure mode wireless network 150 is depicted. The infrastructure mode wireless network 150 includes three client stations 154-1, 154-2, and 154-3, which all communicate with a common device, access point (AP) 156.
The client stations 154 and AP 156 together form a BSS. In various implementations, the BSSID is equal to the MAC address of AP 156. AP 156 serves as an intermediary for one client station 154 to communicate with another client station 154. AP 156 may also communicate with a wired network 158, which in turn may communicate with other BSS's (not shown) or other networks, such as the Internet 160.
AP 156 periodically transmits a beacon to the client stations 154 within the BSS. The beacon is a packet or frame of information that informs the client stations 154 about the capabilities of the BSS and coordinates communication within the BSS. The beacon includes the BSSID, the beacon interval, and a delivery traffic indication message (DTIM). The DTIM serves a function similar to the ATIM of an ad-hoc network.
Referring now to FIG. 3, a functional block diagram of an exemplary mesh network 200 is depicted. The mesh network 200 includes specialized mesh portals 202-1 and 202-2, which communicate with a network 204, such as the Internet. The mesh network 200 also includes mesh points 208-1, 208-2, 208-3, 208-4, 208-5, and 208-6. The mesh points 208 communicate with each other according to their physical proximity and signal strength. The mesh points 208 interface with the mesh portals 202 to gain access to the network 204. The mesh portals 202 may relay traffic between each other via the network 204.